Potential For 100ft. Waves On NW Coast Now Seems A Possibility

Japan’s megaquake and tsunami last year has Northwest emergency planners wondering whether a similar earthquake here would unleash a much larger tsunami than anticipated.

By Sandi Doughton

Seattle Times science reporter

Enlarge this photoNOAA

A computer simulation shows how a tsunami generated by a magnitude 9 earthquake off the Northwest Coast would spread across the Pacific. Scientists are asking whether the massive waves triggered by last year’s Japanese quake mean a quake here could create bigger-than-expected tsunamis. Darker colors indicate bigger waves.

Graphic: Cascadia subduction zone

The Cascadia subduction zone is the boundary where the Juan de Fuca plate dives beneath the North American plate. After last year’s Japan megaquake, some scientists and emergency planners now wonder whether an earthquake along this zone could trigger a tsunami much larger than originally predicted.

The specter of 30-foot waves slamming into the Northwest coast used to be about the worst thing emergency managers in Washington and Oregon could imagine. Now, a year after Japan’s megaquake and tsunami, they’re wondering whether their nightmares were bad enough.

Scientists and planners are reconsidering the region’s tsunami risk in light of the massive walls of water that swept nearly 20,000 people to their deaths on the day the Japanese simply call 3-11. The tsunami reached 130 feet high in some places, taking everyone by surprise.

Levels that extreme are unlikely in the Pacific Northwest, but experts say it’s possible some parts of our coast could be hit by waves of up to 100 feet the next time the offshore fault called the Cascadia subduction zone snaps.

“That is definitely something we need to be prepared for,” said Vasily Titov, head of tsunami modeling at the National Oceanic and Atmospheric Administration in Seattle. “Underestimating kills people … and the Japan event emphasized that in a very vivid way.”

Researchers are still unraveling the disaster and digesting its lessons. At the same time, the Obama administration proposes to cut $4.6 million from NOAA’s tsunami programs as part of a push to reduce government spending and the deficit.

State officials fear the cuts could undermine the safety of seaside communities.

“There will be serious consequences for our continued ability to maintain the level of preparedness on the coast today,” said John Schelling, earthquake and tsunami program manager for Washington’s Emergency Management Division.

NOAA officials say the cuts will mostly affect funding for state programs, like tsunami education and evacuation signs, and won’t affect the national tsunami detection and warning system.

The federal government boosted funding for tsunami programs after the 2004 Indian Ocean tsunami killed more than 230,000 people. Since then, researchers have improved computer models that simulate how tsunamis spread.

States used the results to map danger zones for scores of coastal communities in Washington, Oregon, Northern California and Alaska. Scenarios for the Pacific Northwest generally yield maximum wave heights of about 30 feet.

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